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Fluoroform is the chemical compound with the formula CHF3. It is one of the "haloforms", a class of compounds with the formula CHX3 (X = halogen). Fluoroform is used in diverse niche applications and is produced as a by-product of the manufacture of Teflon. Fluoroform is also generated biologically in small amounts apparently by decarboxylation of trifluoroacetic acid.[1]
Additional physical properties 编辑
| Property | Value |
|---|---|
| Density (ρ) at -100 °C (liquid) | 1.52 g/cm3 |
| Density (ρ) at -82.1 °C (liquid) | 1.431 g/cm3 |
| Density (ρ) at -82.1 °C (gas) | 4.57 kg/m3 |
| Density (ρ) at 0 °C (gas) | 2.86 kg/m3 |
| Density (ρ) at 15 °C (gas) | 2.99 kg/m3 |
| Dipole moment | 1.649 D |
| Critical pressure (pc) | 4.816 MPa (48.16 bar) |
| Critical temperature (Tc) | 25.7 °C (299 K) |
| Critical density (ρc) | 7.52 mol/l |
| Compressibility factor (Z) | 0.9913 |
| Acentric factor (ω) | 0.26414 |
| Viscosity (η) at 25 °C | 14.4 μPa.s (0.0144 cP) |
| Molar specific heat at constant volume (CV) | 51.577 J.mol-1.K-1 |
| Latent heat of vaporization (lb) | 257.91 kJ.kg-1 |
Industrial applications 编辑
CHF3 is used in the semiconductor industry in plasma etching of silicon oxide and silicon nitride.
As a refrigerant, CHF3 is known as R-23 or HFC-23.
HFC-23 is also used as a replacement for Halon 1301[cfc-13b1] in fire suppression systems as a total flooding gaseous fire suppression agent. It is also used as a low temperature refrigerant (replacement for Chlorotrifluoromethane (cfc-13). It is a byproduct of its manufacture. When used as a fire suppressant, the chemical carries the DuPont trade name, FE-13. CHF3 is recommended for this application because of its low toxicity, its low reactivity, and its high density.
CHF3 is a potent greenhouse gas. The secretariat of the Clean Development Mechanism estimates that a ton of HFC-23 in the atmosphere has the same effect as 11,700 tons of carbon dioxide. The atmospheric lifetime is 260 years.[2] According to researchers, it is the most abundant of hydrofluorocarbons (HFCs). Its usage has been regulated since December 1997 at Kyoto climate conference.
Chemistry 编辑
It was first obtained by Meslans in the violent reaction of iodoform with dry silver fluoride in 1894. [3] The reaction was improved by Otto Ruff by substitution of silver fluoride by a mixture of mercury fluoride and calcium fluoride.[4] The exchange reaction works with iodoform and bromoform, and the exchange of the first two halogen atoms by fluorine is vigorous. By changing to a two step process, first forming a bromodifluoro methane in the reaction of antimony trifluoride with bromoform and finishing the reaction with mercury fluoride the first efficient synthesis method was found by Henne.[5]
Organic chemistry 编辑
CHF3 is a reagent to generate CF3- reagents by deprotonation. The molecule is weakly acidic with a pKa = 25–28. It is a precursor to CF3Si(CH3)3[6]
See also 编辑
References 编辑
- ^ Kirschner, E., Chemical and Engineering News 1994, 8.
- ^ Refrigerant Data Summary. Engineered Systems. 2001, 18: 74–88.
- ^ Meslans M. M. Recherches sur quelques fluorures organiques de la série grasse. Annales de chimie et de physique. 1894, 7 (1): 346–423.
- ^ Henne A. L. Fluoroform. Journal of the American Chemical Society. 1937, 59 (7): 1200–1202. doi:10.1021/ja01286a012.
- ^ Henne A. L. Fluoroform. Journal of the American Chemical Society. 1937, 59 (7): 1200–1202. doi:10.1021/ja01286a012.
- ^ Rozen, S.; Hagooly, A. "Fluoroform" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi: 10.1002/047084289
- McBee E. T. Fluorine Chemistry. Industrial & Engineering Chemistry. 1947, 39 (3): 236–237. doi:10.1021/ie50447a002.
- Oram D. E., Sturges W. T., Penkett S. A., McCulloch A., Fraser P. J. Growth of fluoroform (CHF3, HFC-23) in the background atmosphere. Geophysical Research Letters. 1998, 25 (1): 236–237. doi:10.1029/97GL03483.
- McCulloch A. Fluorocarbons in the global environment: a review of the important interactions with atmospheric chemistry and physics. Journal of Fluorine Chemistry. 2003, 123 (1): 21–29. doi:10.1016/S0022-1139(03)00105-2.